Structured anodes for lithium-based energy storage devices

ABSTRACT

An anode for an energy storage device includes a current collector. The current collector includes: i) an electrically conductive substrate including a first electrically conductive material; ii) a plurality of electrically conductive structures in electrical communication with the electrically conductive substrate, wherein each electrically conductive structure includes a second electrically conductive material; and iii) a metal oxide coating. The metal oxide coating includes one or both of: a) a first metal oxide material in contact with the electrically conductive substrate; or b) a second metal oxide material in contact with the electrically conductive structures; or both (a) and (b). The anode further includes lithium storage coating overlaying the metal oxide coating, the lithium storage layer including a total content of silicon, germanium, or a combination thereof, of at least 40 atomic %. The electrically conductive structures are at least partially embedded within the lithium storage coating.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of priority of U.S. ProvisionalApplication No. 62/889,351, filed Aug. 20, 2019, which is incorporatedherein by reference in its entirety for all purposes.

TECHNICAL FIELD

The present disclosure relates to lithium ion batteries and relatedenergy storage devices.

BACKGROUND

Silicon has been proposed as a potential material for lithium-ionbatteries to replace the conventional carbon-based anodes which have astorage capacity that is limited to ˜370 mAh/g. Silicon readily alloyswith lithium and has a much higher theoretical storage capacity (˜3600to 4200 mAh/g at room temperature) than carbon-based anodes. However,insertion and extraction of lithium into the silicon matrix causessignificant volume expansion (>300%) and contraction. This can result inrapid pulverization of the silicon into small particles and electricaldisconnection from the current collector.

The industry has recently turned its attention to nano- ormicro-structured silicon to reduce the pulverization problem, i.e.,silicon in the form of spaced apart nano- or micro-wires, tubes,pillars, particles, and the like. The theory is that making thestructures nano-sized avoids crack propagation and spacing them apartallows more room for volume expansion, thereby enabling the silicon toabsorb lithium with reduced stresses and improved stability compared to,for example, macroscopic layers of bulk silicon.

Despite research into structured silicon approaches, such batteriesbased primarily on silicon have yet to make a large market impact due tounresolved problems.

SUMMARY

There remains a need for anodes for lithium-based energy storage devicessuch as Li-ion batteries that are easy to manufacture, robust tohandling, high in charge capacity and amenable to fast charging, forexample, at least 1C. These and other needs are addressed by theembodiments described herein.

In accordance with an embodiment of this disclosure, an anode for anenergy storage device is provided that includes a current collector anda lithium storage coating. The current collector includes: i) anelectrically conductive substrate including a first electricallyconductive material; ii) a plurality of electrically conductivestructures in electrical communication with the electrically conductivesubstrate, wherein each electrically conductive structure includes asecond electrically conductive material; and iii) a metal oxide coating.The metal oxide coating includes one or both of: a) a first metal oxidematerial in contact with the electrically conductive substrate; or b) asecond metal oxide material in contact with the electrically conductivestructures; or both (a) and (b). The anode further includes lithiumstorage coating overlaying the metal oxide coating, the lithium storagelayer including a total content of silicon, germanium, or a combinationthereof, of at least 40 atomic %. The electrically conductive structuresare at least partially embedded within the lithium storage coating.

The present disclosure provides anodes for energy storage devices thatmay have one or more of at least the following advantages relative toconventional anodes: improved stability at aggressive ≥1C chargingrates; higher overall areal charge capacity; higher charge capacity pergram of silicon; improved physical durability; simplified manufacturingprocess; and more reproducible manufacturing process.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1A-1C are cross-sectional views illustrating the making of ananode according to some embodiment of the present disclosure.

FIGS. 2A-2E are cross-sectional views illustrating the making of ananode according to some embodiment of the present disclosure.

FIGS. 3A-2C are cross-sectional views illustrating the making of ananode according to some embodiment of the present disclosure.

FIGS. 4A-4C are cross-sectional views illustrating the making of ananode according to some embodiment of the present disclosure.

FIG. 5A is a plan view of a current collector precursor according tosome embodiment of the present disclosure.

FIG. 5B is a cross-sectional view of a current collector precursor takenalong cut line B-B of FIG. 5A.

FIG. 5C is a cross-sectional view of a current collector precursor takenalong cut line C-C of FIG. 5A.

FIGS. 6A-6F are cross-sectional views of current collector precursorsillustrating various shapes available for the electrically conductivestructures according to some embodiments of the present disclosure.

FIG. 7 is a plan view of a current collector precursor illustratingvarious shapes for the electrically conductive structures according tosome embodiments of the present disclosure.

FIG. 8 is a schematic cross-sectional view of a battery according tosome embodiments of the present disclosure.

DETAILED DESCRIPTION

It is to be understood that the drawings are for purposes ofillustrating the concepts of the disclosure and may not be to scale.Various aspects of anodes of the present disclosure, including metaloxide layers, deposition of lithium storage material, additional layersand methods are described in co-pending U.S. patent application Ser.Nos. 16/285,842, 16/909,008, 16/991,613, 16/991,623, and 16/991,626, theentire contents of which are incorporated by reference for all purposes.

Anode Overview

FIGS. 1A-1C are cross-sectional views illustrating the fabrication of ananode according to some embodiments of the present disclosure. In FIG.1A, a current collector precursor 101′ includes an electricallyconductive substrate 103 and a plurality of electrically conductivestructures 104 in electrical communication with the electricallyconductive substrate 103, for example, through direct physical contact.The electrically conductive substrate 103 includes a first electricallyconductive material and each of the plurality of electrically conductivestructures comprises a second electrically conductive material, whichmay be the same as, or different than, the first electrically conductivematerial. Materials, methods of making, and other features of thecurrent collector precursor 101′ are discussed later.

In FIG. 1B, a metal oxide coating is provided in contact with thecurrent collector precursor 101′ to form current collector 101. In thepresent embodiment, the metal oxide coating includes a first metal oxidematerial 105 formed in contact with the electrically conductivesubstrate 103 and a second metal oxide material 106 formed in contactwith electrically conductive structures 104. In some embodiments, thefirst metal oxide material is provided as a coating or layer over mostof the available surface area of the electrically conductive substratenot otherwise occupied by the electrically conductive structures.Materials, methods of forming, and other features of the metal oxidematerial are discussed later.

In FIG. 1C, a lithium storage coating 107 having an outer surface 107′is deposited over the current collector 101 and in contact with themetal oxide coating (the first metal oxide material 105 and second metaloxide material 106) to form anode 100. The electrically conductivestructures 104 are at least partially embedded within the lithiumstorage coating 107. That is, the lithium storage coating includes aplurality of concavities with an electrically conductive structurepresent in each concavity. As shown in FIG. 1C, the electricallyconductive structures 104 may be fully embedded within the lithiumstorage coating 107. In some embodiments, as discussed later, thelithium storage coating may include porous silicon deposited by a CVDprocess, for example, a PECVD process. In some embodiments, thethickness of the lithium storage coating may be characterized by thedistance between the lithium storage coating outer surface 107′ to thenearest metal oxide material. The thickness may vary along thestructure.

FIGS. 2A-2C are cross-sectional views illustrating the fabrication of ananode according to some embodiments of the present disclosure. In FIG.2A, a current collector precursor 201′ includes an electricallyconductive substrate 203 and a plurality of electrically conductivestructures 204 in electrical communication with the electricallyconductive substrate 203, for example, through direct physical contact.The electrically conductive substrate 203 includes a first electricallyconductive material and each of the plurality of electrically conductivestructures comprises a second electrically conductive material, whichmay be the same as, or different than, the first electrically conductivematerial. Materials, methods of making, and other features of thecurrent collector precursor 201′ are discussed later.

In FIG. 2B, a metal oxide coating is provided in contact with thecurrent collector precursor 201′ to form current collector 201. In thepresent embodiment, the metal oxide coating includes a second metaloxide material 206 formed in contact with electrically conductivestructures 204. Unlike FIG. 1, there is no substantial amount metaloxide (e.g., less than 0.01 μm thick if any at all) in contact with theelectrically conductive substrate. Materials, methods of forming, andother features of the metal oxide material are discussed later.

In FIG. 2C, a lithium storage coating 207 may be deposited to form anode200. The lithium storage coating 207 may overlay and be in contact withthe second metal oxide material 206. The electrically conductivestructures 204 may be at least partially embedded within the lithiumstorage coating 207. The electrically conductive structures 204 may befully embedded within the lithium storage coating 207. In someembodiments, as discussed later, the lithium storage coating may includeporous silicon deposited by a CVD process, for example, a PECVD process.In some embodiments, as shown in FIG. 2C, the lithium storage coatingmay selectively deposit on the second metal oxide material 206 and doesnot form an adherent coating over the electrically conductive substrateIn some embodiments, the rate of CVD reaction may be faster at thesecond metal oxide material surface than at the electrically conductivesubstrate surface and may continue to be faster at the surface of thelithium storage coating than at the electrically conductive substrate.

In some embodiments, as shown in FIG. 2D, anode 200D is formed wheresome lithium storage material may also deposit onto the bareelectrically conductive substrate, for example, as a lithium storagelayer 209, which may have a similar composition to lithium storagecoating 207. In some embodiments, the electrically conductive structuresand lithium storage coating 207 may physically assist in holding thelithium storage layer 209 between such structures in place to maintainadherence and electrical continuity with the electrically conductivesubstrate.

In some embodiments, as shown in FIG. 2E, anode 200E is formed where aplurality of lithium storage nanostructures 208 may be formed on theelectrically conductive substrate concurrently with deposition of thelithium storage coating 207 over the second metal oxide. For example,silicon-containing nanowires and microwires can be grown fromnickel-containing electrically conductive substrates. In someembodiments, the nanowires and microwires may have a nickel silicidecore and an amorphous silicon shell. Some non-limiting methods ofgrowing lithium storage filaments on metals are described in U.S. Pat.Nos. 9,325,014 and 8,257,866, the entire contents of which areincorporated by reference for all purposes.

FIGS. 3A-3C are cross-sectional views illustrating the fabrication of ananode according to some embodiments of the present disclosure. In FIG.3A, a current collector precursor 301′ includes an electricallyconductive substrate 303 and a plurality of electrically conductivestructures 304 in electrical communication with the electricallyconductive substrate 303, for example, through direct physical contact.The electrically conductive substrate 303 includes a first electricallyconductive material and each of the plurality of electrically conductivestructures comprises a second electrically conductive material, whichmay be the same as, or different than, the first electrically conductivematerial. Materials, methods of making, and other features of thecurrent collector precursor 301′ are discussed later.

In FIG. 3B, a metal oxide coating is provided in contact with thecurrent collector precursor 301′ to form current collector 301. In thepresent embodiment, the metal oxide coating includes a first metal oxidematerial 305 formed in contact with the electrically conductivesubstrate 303. Unlike FIG. 1, there is no substantial amount of metaloxide coating (e.g., less than 0.002 μm thick if any at all) in contactwith electrically conductive structures 304. In some embodiments, thefirst metal oxide material is provided as a coating or layer over mostof the available surface area of the electrically conductive substratenot otherwise occupied by the electrically conductive structures.Materials, methods of forming, and other features of the metal oxidematerial are discussed later.

In FIG. 3C, a lithium storage coating 307 is deposited over the currentcollector 301 and in contact with the first metal oxide material 305 toform anode 300. The electrically conductive structures 304 are at leastpartially embedded within the lithium storage coating 307. That is, thelithium storage coating includes a plurality of concavities with anelectrically conductive structure present in each concavity. As shown inFIG. 3C, the electrically conductive structures 304 may be fullyembedded within the lithium storage coating 307. In some embodiments, asdiscussed later, the lithium storage coating may include porous silicondeposited by a CVD process, for example, a PECVD process. In someembodiments, as shown in FIG. 3C, the lithium storage coating mayselectively deposit on the first metal oxide material 305 and does notform an adherent coating over the electrically conductive structures. Insome embodiments, the rate of the CVD reaction may be faster at thefirst metal oxide material surface than at the electrically conductivestructures and may continue to be faster at the surface of the lithiumstorage coating than at the electrically conductive structures.

FIGS. 4A-C are cross-sectional views according to some embodiments ofthe present disclosure. In FIG. 4A, current collector 401 includes anelectrically conductive substrate 403, and a plurality of electricallyconductive structures 404 in electrical communication with electricallyconductive substrate 403. A first metal oxide material 405 is in contactwith electrically conductive substrate 403 in regions not occupied bythe electrically conductive structures 404.

In FIG. 4B, a lithium storage coating 407 may be deposited to form anode400B. The lithium storage coating 407 may overlay and be in contact withthe first metal oxide material 405. The electrically conductivestructures 404 are partially embedded within the lithium storage coating407, but also extend beyond the lithium storage coating. In someembodiments, as discussed later, the lithium storage coating may includeporous silicon deposited by a CVD process, for example, a PECVD process.In some embodiments, the lithium storage coating selectively deposits onthe first metal oxide material 405. In some embodiments, the rate of aCVD reaction may be faster at the first metal oxide material surfacethan at the electrically conductive structures and may continue to befaster at the surface of the lithium storage coating than at theelectrically conductive structure.

In some embodiments and as shown in FIG. 4C, after forming anode 400B,deposition conditions may be altered (for example, temperature may beincreased) to induce growth of lithium storage filaments 408 on theelectrically conductive structures 404, forming hybrid anode 400C havingboth a lithium storage coating(s) and lithium storage filaments. Forexample, silicon-containing nanowires and microwires can be grown onnickel-containing electrically conductive structures. In someembodiments, the nanowires and microwires may have a nickel silicidecore and an amorphous silicon shell. Some non-limiting methods ofgrowing lithium storage filaments are described in U.S. Pat. Nos.9,325,014 and 8,257,866, the entire contents of which are incorporatedby reference for all purposes. Additional lithium storage coatingmaterial may also deposit over the first metal oxide material 405 whilethe lithium storage filaments are growing.

Current Collector

In some embodiments, the electrically conductive substrate includes afirst electrically conductive material. The first electricallyconductive material may have a conductivity of at least 100 S/m,alternatively at least 10³ S/m, alternatively at least 10⁶ S/m,alternatively at least 10⁷ S/m, In some embodiments, the firstelectrically conductive material may include a metal. In someembodiments, the metal may be a transition metal or an alloy including atransition metal. In some embodiments, the transition metal is copper,nickel, iron, chromium, or titanium. In some embodiment, the firstelectrically conductive material may include stainless steel. In someembodiments, the first electrically conductive material includes anelectrically conductive carbon, such as carbon black, carbon nanotubes,graphene, graphene oxide, reduced graphene oxide, and graphite. In someembodiments the electrically conductive substrate may be in the form ofa mesh or some other 3-dimensional structure, a foil or a sheet ofconductive material, or a layer deposited onto an insulating substrate(e.g., a polymer sheet or ceramic sheet coated with conductive materialsuch as nickel or copper, optionally on both sides).

In some embodiments, the electrically conductive substrate includes amesh or sheet of electrically conductive carbon, including but notlimited to, those formed from bundled carbon nanotubes or nanofibers. Insome embodiments, such carbon-based electrically conductive substratesmay include a surface layer of a conductive metal, e.g., nickel, copper,zinc, titanium, or the like. In some embodiments, the conductive metalsurface layer may be applied by electrolytic or electroless platingmethods.

In some embodiments, the electrically conductive substrate has anaverage thickness of at least 0.1 μm, alternatively at least 1 μm,alternatively at least 5 μm. In some embodiments, the electricallyconductive substrate has an average thickness in a range of 0.1 μm to 1μm, alternatively 1 μm to 2 μm, alternatively 2 μm to 5 μm,alternatively 5 μm, to 10 μm, alternatively 10 μm to 15 μm,alternatively 15 μm to 20 μm, alternatively 20 μm to 30 μm,alternatively 30 μm to 50 μm, alternatively 50 μm to 100 μm, or anycombination of contiguous ranges thereof.

Referring to FIG. 5A, there is a plan view of current collectorprecursor 501′ having a plurality of electrically conductive structures504 in electrical communication (e.g. in contact) with electricallyconductive substrate 503. Each of the plurality of electricallyconductive structures 504 is characterized by a height H measured fromthe electrically conductive substrate 503 to its end along a firstelectrically conductive structure axis. The electrically conductivestructures may be further characterized by a width W and a length L,measured parallel to the electrically conductive substrate surface. Insome embodiments, length L is approximately the same as W, and may bemeasured in a direction approximately orthogonal to the width. FIG. 5Bshows a cross-sectional view of current collector precursor 501′ alongcut line B-B to illustrate H and W of electrically conductive structure504. FIG. 5C shows a cross-sectional view of current collector precursor501′ along cut line C-C to illustrate H and L of the electricallyconductive structure 504. In general, W represents the shortestdimension of electrically conductive structure 504 in plan view (FIG.5A) and corresponds to the widest portion of its cross-section (FIG.5B).

The electrically conductive structures may each have an aspect ratiodefined by height H divided by width W that is generally at least 1,alternatively at least 2, alternatively at least 5, alternatively atleast 10. In some embodiments, the aspect ratio may be in a range of 1to 2, alternatively 2 to 5, alternatively 5 to 10, alternatively 10 to20, alternatively 20 to 50, alternatively 50 to 100, alternatively 100to 200, alternatively 200 to 500, alternatively in a range of 500 to1000, or any combination of contiguous ranges thereof. There is noparticular limitation on the length L of the electrically conductivestructure other than it is by definition at least the same as width W,or greater. Referring again to FIG. 5A, a portion of the surface area ofthe electrically conductive substrate is in occupied by or in contactwith the electrically conductive structures (“occupied area”). In someembodiments, the occupied area is at least 1% and less than 99%. In someembodiments, the occupied area is in a range of 2% to 10%, alternatively10% to 20%, alternatively 20% to 30%, alternatively 30% to 40%,alternatively 40% to 50%, alternatively 50% to 60%, alternatively 60% to70%, alternatively 70% to 80%, alternatively 80% to 90%, alternatively90% to 98%, or any combination of contiguous ranges thereof.

In some embodiments, the surface area of the electrically conductivesubstrate includes 2 to 5 electrically conductive structures per squarecentimeter, alternatively 5 to 10, alternatively 10 to 50, alternatively50 to 100, alternatively 100 to 500, alternatively 500 to 1000,alternatively 1000 to 10,000, alternatively 5000 to 10,000,alternatively 10,000 to 100,000, alternatively 100,000 to 1,000,000,alternatively 1,000,000 to 10,000,000 electrically conductivestructures, or an any combination of contiguous ranges thereof. In someembodiments, the surface area of the electrically conductive substrateincludes at least 5 electrically conductive structures per squarecentimeter, alternatively at least 10, alternatively at least 100,alternatively at least 1000, alternatively at least 10,000,alternatively at least 100,000, or alternatively at least 1,000,000electrically conductive structures.

In some embodiments, the height H of each of the plurality theelectrically conductive structures may be at least 1 μm, alternativelyat least 5 μm, alternatively at least 10 μm, alternatively at least 20μm. In some embodiments, the average height H of the electricallyconductive structures is in a range of 1 μm to 2 μm, alternatively 2 μmto 5 μm, alternatively 5 μm to 10 μm, alternatively 10 μm to 15 μm,alternatively 15 μm to 20 μm, alternatively 20 μm to 50 μm,alternatively 50 μm to 100 μm, or any combination of contiguous rangesthereof. In some embodiments, the electrically conductive structure hasa cross-sectional width of at least 0.002 μm, alternatively at least0.005 μm, alternatively at least 0.010 μm, alternatively at least 0.10μm, alternatively at least 1.0 μm, alternatively at least 10 μm,alternatively at least 20 μm.

There are a wide variety of shapes the electrically conductivestructures may take, including but not limited to, wires, pillars,tubes, ridges, or dendrites. FIGS. 6A-6H illustrate cross-sectionalviews of some non-limiting examples of electrically conductivestructures 604-a-604-h provided over electrically conductive substrate603-a-603-h. Height H and width W are also noted. In FIG. 6A, theelectrically conductive structures 604-a may have a triangular shape incross-section. Such structures may for example may be conical orpyramidal. In FIG. 6B, the electrically conductive structures 604-b mayhave a trapezoidal shape in cross-section. In FIG. 6C, the electricallyconductive structures 604-c may have an inverted trapezoidal shape incross-section. In FIG. 6D, the electrically conductive structures 604-dmay have a circular, oval, or ellipsoidal shape in cross-section. InFIG. 6E, the electrically conductive structures 604-e may have aright-triangular or wedge shape in cross-section. In FIG. 6F, theelectrically conductive structures 604-f may have a base-and-pillarshape in cross-section. With a base-and-pillar shape, the aspect ratiomay be in terms of the pillar width instead of the base width. In FIG.6G, electrically conductive structures 604-g may have a dendritic orbranched shape in cross section. For such structures, W is defined bythe maximum width of a branch or “trunk” (the portion in contact withthe electrically conductive substrate), not the spread of branches. InFIG. 6H, electrically conductive structures 604-h may have an irregularor nodular shape in cross-section.

FIG. 7 illustrates a plan view of some additional non-limiting examplesof variously-shaped electrically conductive structures 704-a-704-k, overelectrically conductive substrate 703 that may make up current collectorprecursor 701′. For convenience only one example of each electricallyconductive structure is shown. A current collector precursor may includejust one type of shape or a plurality of shapes. The cross-sectionalviews of FIG. 6 may be combined with almost any of the structures ofFIG. 7. The plan view shapes may appear circular (704-a), oblong orelliptical (704-b), polygonal such as hexagonal (704-c), square (704-d),branched or dendritic (704-e), tubular (704-f), crescent (704-g),intersected such as a cross (704-h) or as part of an interconnected mesh(704 i), or as a long ridge, that may be straight (704-j) or sinusoidal(704-k). In some embodiments, when the electrically conductivestructures are oblong or ridge-like, they may be provided parallel to anaxis of winding, e.g., when assembling jelly-roll type batteries in inroll-to-roll manufacturing methods.

The electrically conductive structures may include a second electricallyconductive material that may be substantially the same as or differentthan the first electrically conductive material. In some embodiments,when the electrically conductive material includes a metal“substantially the same as” may mean that the atomic % of each elementof the first electrically conductive material is within 2 atomic % ofthe second electrically conductive material. In some embodiments, whenthe electrically conductive materials include conductive carbonmaterials, “substantially the same” may mean that the weight % of eachform of conductive carbon material of the first electrically conductivematerial is within 2 weight % of each form of conductive carbon materialin the second electrically conductive material. The second electricallyconductive material may have a conductivity of at least 1 S/m,alternatively, at least 10 S/m, alternatively at least 100 S/m,alternatively at least 10³ S/m, alternatively at least 10⁶ S/m,alternatively at least 10⁷ S/m, In some embodiments, the conductivity ofthe second electrically conductive material is lower than theconductivity of the first electrically conductive material. In someembodiments, the second electrically conductive material may include ametal. In some embodiments, the metal may be a transition metal or analloy including a transition metal. In some embodiments, the transitionmetal is copper, nickel, iron, chromium, or titanium. In someembodiments, the second electrically conductive material may include ametal silicide. In some embodiment, the second electrically conductivematerial includes an electrically conductive carbon, such as carbonblack, carbon nanotubes, graphene, graphene oxide, reduced grapheneoxide, and graphite. In some embodiments, the electrically conductivestructures include carbon nanotubes. In some embodiments, the carbonnanotubes may be embedded in the electrically conductive substrate, forexample, as disclosed in U.S. Pat. Nos. 9,257,704 or 10,008,717, theentire contents are incorporated herein for all purposes. In someembodiments, the second electrically conductive material may include aan electrically conductive doped oxide, including but not limited to,indium-doped tin oxide (ITO) or an aluminum-doped zinc oxide (AZO).

In some embodiments, electrically conductive metal structures may bepattern deposited over an electrically conductive substrate by a PVDmethod such as evaporation through a shadow mask. In some embodimentsmetallic electrically conductive structures may be electrolytically orelectrolessly plated through a patterned resist (e.g. a photoresist)overlaying the electrically conductive substrate followed by removal ofthe resist. Such photolithographic methods are well known in the art. Insome embodiments, metallic electrically conductive structures may berandomly grown by high-current or pulse electroplating. In someembodiments, electrically conductive structures may be formed bypatterned etching the electrically conductive substrate, for example,using a patterned resist or photoresist to block etching in the desiredpattern. Etching may be include a “wet” chemical etchant, or a dryetching process such as a plasma etching method. Since the electricallyconductive structures are formed from the electrically conductivesubstrate, the first and second electrically conductive materials may bethe same. Etching can readily produce electrically conductive structureshaving an aspect ratio of 1, but higher aspect ratios may requireanisotropic etching methods as is known in the art.

In some embodiments, electrically conductive structures may be depositedor grown in the form of filaments, nanowires, or the like. Methods offorming metal filaments and nanowires or carbon nanotubes are well knownin the art, including but not limited to CVD-based methods usingfilament growth promoting materials. In some embodiments, a filamentgrowth promoting material is provided over the electrically conductivesubstrate. In some embodiments, the filament growth promoting materialis a vapor-liquid-solid (VLS) filament growth promoting material. Insome embodiments, the filament growth promoting material is provided bya substantially continuous layer over the electrically conductivesubstrate. In some embodiments, the filament growth promoting materialmay be provided as a patterned layer or as a layer of discontinuousislands over the electrically conductive substrate. In some embodiments,the electrically conductive substrate itself includes the filamentgrowth promoting material. Non-limiting examples of filament growthmaterials may include non-refractory transition metals and their alloys.The growth promoting material may include, for example, nickel, gold,palladium, platinum, ruthenium, aluminum, indium, gallium, tin, or iron,or their alloys. The temperature depends on the growth material andfilament precursor gas, but in some embodiments may be at least 100° C.,alternatively from 100° C. to 200° C., alternatively from 200° C. to300° C., 300° C., alternatively from 300° C. to 400° C., alternativelyfrom 400° C. to 500° C., alternatively from 500 ° C. to 600° C.,alternatively from 600° C. to 700° C., alternatively from 700° C. to800° C., alternatively from 800° C. to 900° C., or any combination ofcontiguous ranges thereof.

In some embodiments, the electrically conductive structures include ametal silicide or a metal-germanium alloy. The silicide or germaniumalloy may include a transition metal including, but not limited to,nickel or copper. In some embodiments, the silicide or germanium alloymay be deposited in the form of filaments using a CVD process and VLSgrowth materials along with a silicon- or germanium-containing precursorgas.

In some embodiments, the electrically conductive structures may includenanostructures. The term “nanostructure” herein generally refers to astructure having at least one cross-sectional dimension that is lessthan about 2,000 nm, other than a dimension approximately normal to anunderlying substrate (such as a layer thickness) and excludingdimensions caused by random pores. Similarly, the terms “nanowires”,“nanopillars”, and “nanotubes” refers to wires, pillars, and tubes,respectively, at least a portion of which, have a diameter of less than2,000 nm.

Unless otherwise noted, the discussion below regarding metal oxidematerials and methods of forming them are generally applicable to boththe first metal oxide material and the second metal oxide material.

The metal oxide material may be stoichiometric or non-stoichiometric.The metal oxide may include a mixture of metal oxides havinghomogeneously or heterogeneously distributed oxide stoichiometries,mixtures of metals or both. The metal oxide material should besufficiently electrically conductive to allow transfer of electricalcharge between the current collector and the lithium storage coating. Insome embodiments, the metal oxide material may include dopants orregions of unoxidized metal that promote electrical conductivity.

In some embodiments, the metal oxide material includes a transitionmetal oxide, e.g., an oxide of nickel, zinc, titanium, or copper. Insome embodiments, the metal oxide material may include an alkali metaloxide or an alkaline earth metal oxide. In some embodiments the metaloxide material includes an oxide of lithium. The metal oxide materialmay include a mixture of metals. For example, an “oxide of nickel” mayoptionally include other metals in addition to nickel. In someembodiments, the metal oxide material includes an oxide of an alkalimetal (e.g., lithium or sodium) or an alkaline earth metal (e.g.,magnesium or calcium) along with an oxide of a transition metal (e.g.,nickel, zinc, titanium, or copper). The metal oxide material may includea stoichiometric metal oxide, a non-stoichiometric metal oxide, or both.In some embodiments, the metal within the metal oxide may exist inmultiple oxidation states. In some embodiments the metal oxide may havea gradient of oxygen content where the atomic % of oxygen near theelectrically conductive substrate or the electrically conductivestructures is less than the atomic % away electrically conductivesubstrate or the electrically conductive structures, respectively.

In some embodiments, the first metal oxide material may have an averagethickness of at least 0.005 μm, alternatively at least 0.01 μm,alternatively at least 0.02 μm, alternatively at least 0.05 μm,alternatively 0.1 μm, alternatively at least 0.2 μm, alternatively atleast 0.5 μm. In some embodiments, the first metal oxide material has anaverage thickness in a range of about 0.005 μm to about 0.01 μm,alternatively about 0.01 μm to about 0.02 μm, alternatively about 0.02μm to about 0.05 μm, alternatively about 0.05 μm to about 0.1 μm,alternatively about 0.1 μm to about 0.2 μm, alternatively about 0.2 μmto about 0.5 μm, alternatively about 0.5 μm to about 1 μm, alternativelyabout 1 μm to about 2 μm, alternatively about 2 μm to about 5 μm,alternatively about 5 μm to about 1 μm, or any combination of contiguousranges thereof.

In some embodiments, the second metal oxide material may have an averagethickness of at least 0.001 μm, alternatively at least 0.002 μm,alternatively at least 0.005 μm , alternatively at least 0.01 μm,alternatively at least 0.02 μm, alternatively at least 0.05 μm,alternatively 0.1 μm, alternatively at least 0.2 μm, alternatively atleast 0.5 μm. In some embodiments, the second metal oxide material hasan average thickness in a range of about 0.005 μm to about 0.01 μm,alternatively about 0.01 μm to about 0.02 μm, alternatively about 0.02μm to about 0.05 μm, alternatively about 0.05 μm to about 0.1 μm,alternatively about 0.1 μm to about 0.2 μm, alternatively about 0.2 μmto about 0.5 μm, alternatively about 0.5 μm to about 1 μm, alternativelyabout 1 μm to about 2 μm, alternatively about 2 μm to about 5 μm,alternatively about 5 μm to about 1 μm, or any combination of contiguousranges thereof. In some embodiments, the thickness of the second metaloxide material is less than the thickness of the first metal oxidematerial.

In some embodiments, the first metal oxide material has a compositionthat is substantially the same as the composition of the second metaloxide material. In some embodiments, “substantially the same as” maymean that the atomic % of each element of the first metal oxide materialis within 2 atomic % of the second metal oxide material.

In some embodiments, the metal oxide material may be directly depositedby atomic layer deposition (ALD), a chemical vapor deposition (CVD)process, evaporation, or sputtering. Such methods may be used to formcurrent collector shown in FIG. 1. In some embodiments, the electricallyconductive substrate or electrically conductive structures includes ametal that can be oxidized. For example, a surface portion of theelectrically conductive substrate or electrically conductive structurescan be thermally oxidized in the presence of oxygen, electrolyticallyoxidized, chemically oxidized in an oxidizing liquid or gaseous mediumor the like to form the metal oxide material at a desired thickness. Ifboth the first and second electrically conductive materials are readilyoxidized, such method may be used to form the current collector shown inFIG. 1. In some embodiments, the first metal oxide material may beselectively oxidized by using a first electrically conductive materialthat is more easily oxidized than the second electrically conductivematerial. Such method may be used to form the current collectors asshown in FIGS. 3 and 4. In some embodiments, the second metal oxidematerial may be selectively oxidized by using a second electricallyconductive material that is more easily oxidized than the firstelectrically conductive material. Such method may be used to form thecurrent collector shown in FIG. 2.

In some embodiments, a metal oxide precursor composition may be appliedand treated to form the metal oxide material. Some non-limiting examplesof metal oxide precursor compositions include sol-gels (metalalkoxides), metal carbonates, metal acetates (including organicacetates), metal hydroxides, and metal oxide dispersions. The metaloxide precursor composition may be thermally treated to form the metaloxide material. In some embodiments, room temperature may be sufficienttemperature to thermally treat the precursor. In some embodiments, ametal oxide precursor composition is thermally treated by exposure to atemperature of at least 50° C., alternatively in a range of 50° C. to150° C., alternatively in a range of 150° C. to 250° C., alternativelyin a range of 250° C. to 350° C., alternatively in a range of 350 ° C.to 450° C., or any combination of these ranges. Thermal treatment timedepends on many factors, but may optionally be at least 0.1 minute,alternatively in a range of 1 to 120 minutes, to form the metal oxidematerial. In some embodiments, thermal treatment may be carried outusing an oven, infrared heating elements, contact with a hot plate orexposure to a flash lamp. In some embodiments, the metal oxide precursorcomposition is treated by exposure to reduced pressure to form the metaloxide, e.g., to drive off solvents or volatile reaction products. Thereduced pressure may be less than 100 Torr, alternatively in a range of0.1 to 100 Torr. Exposure time to the reduced pressure may optionally beat least 0.1 minute, alternatively in a range of 1 to 120 minutes. Insome embodiments, both reduced pressure and thermal treatment may beused.

In some embodiments, the metal oxide material may be formed in the samechamber as, or in line with, a tool used to deposit the lithium storagecoating. Doped metal oxide materials can be formed by adding dopants ordopant precursors during the metal oxide formation step, oralternatively by adding dopants or dopant precursors to a surface overwhich the metal oxide is to be formed. In some embodiments, the metaloxide itself may have some reversible or irreversible lithium storagecapacity. In some embodiments, the reversible capacity of the metaloxide material is lower than that of the lithium storage coating. Insome embodiments, the metal oxide material may be porous. In someembodiments, a porous metal oxide may have a density lower than thedensity of the corresponding non-porous metal oxide. In someembodiments, the density of a porous metal oxide is in a range of 50% to60% of the density of the non-porous metal oxide, alternatively 60% to70%, alternatively 70% to 80%, alternatively 80% to 90%, alternatively90% to 95%, alternatively 95% to 99%, or any combination of contiguousranges thereof.

Lithium Storage Coating

The lithium storage coating includes a material (optionally porous)capable of reversibly incorporating lithium. In some embodiments, thelithium storage coating includes silicon, germanium or a mixture ofboth. In some embodiments, the lithium storage coating includes antimonyor tin. In some embodiments, the lithium storage coating issubstantially amorphous. In some embodiments, the lithium storagecoating includes substantially amorphous silicon. Such substantiallyamorphous storage layers may include a small amount (e.g., less than 20atomic %) of crystalline material dispersed therein. The lithium storagecoating may include dopants such as hydrogen, boron, phosphorous,sulfur, fluorine, aluminum, gallium, indium, arsenic, antimony, bismuth,nitrogen, or metallic elements. In some embodiments the lithium storagecoating may include porous substantially amorphous hydrogenated silicon(a-Si:H), having, e.g., a hydrogen content of from 0.1 to 20 atomic %,or alternatively higher. In some embodiments, the lithium storagecoating may include methylated amorphous silicon. Note that, unlessreferring specifically to hydrogen content, any atomic % metric usedherein for a lithium storage material or coating refers to all atomsother than hydrogen.

In some embodiments, the lithium storage coating includes at least 40atomic % silicon, germanium or a combination thereof, alternatively atleast 50 atomic %, alternatively at least 60 atomic %, alternatively atleast 70 atomic %, alternatively, at least 80 atomic %, alternatively atleast 90 atomic %. In some embodiments, the lithium storage coatingincludes at least 40 atomic % silicon, alternatively at least 50 atomic%, alternatively at least 60 atomic %, alternatively at least 70 atomic%, alternatively, at least 80 atomic %, alternatively at least 90 atomic%, alternatively at least 95 atomic %, alternatively at least 97 atomic%.

In some embodiments, the lithium storage coating includes less than 10atomic % carbon, alternatively less than 5 atomic %, alternatively lessthan 2 atomic %, alternatively less than 1 atomic %, alternatively lessthan 0.5 atomic %. In some embodiments, the lithium storage coatingincludes less than 5% by weight, alternatively less than 1% by weight,of carbon-based binders, carbon nanotubes, graphitic carbon, graphene,graphene oxide, reduced graphene oxide, carbon black, and conductivecarbon.

The lithium storage coating includes voids or interstices (pores), whichmay be random or non-uniform with respect to size, shape anddistribution. Such porosity does not result in, or a result from, theformation of any recognizable nanostructures such as nanowires,nanopillars, nanotubes, nanochannels or the like. In some embodiments,the pores are polydisperse. In some embodiments, when analyzed by SEMcross section, 90% of pores larger than 100 nm in any dimension aresmaller than about 5 μm in any dimension, alternatively smaller thanabout 3 μm, alternatively smaller than about 2 μm. In some embodiments,the lithium storage coating may include some pores that are smaller than100 nm in any dimension, alternatively smaller than 50 nm in anydimension, alternatively smaller than 20 nm in any dimension. In someembodiments the lithium storage coating has an average density in arange of 1.0-1.1 g/cm³, alternatively 1.1-1.2 g/cm³, alternatively1.2-1.3 g/cm³, alternatively 1.3-1.4 g/cm³, alternatively 1.4-1.5 g/cm³,alternatively 1.5-1.6 g/cm³, alternatively 1.6-1.7 g/cm³, alternatively1.7-1.8 g/cm³, alternatively 1.8-1.9 g/cm³, alternatively 1.9-2.0 g/cm³,alternatively 2.0-2.1 g/cm³, alternatively 2.1-2.2 g/cm³, alternatively2.2-2.25 g/cm³, or any combination of contiguous ranges thereof, andincludes at least 40 atomic % silicon, alternatively at least 50 atomic% silicon, alternatively at least 60 atomic % silicon, alternatively atleast 70 atomic % silicon, alternatively 80 atomic % silicon,alternatively at least 90 atomic % silicon, alternatively at least 95atomic % silicon.

In some embodiments, the lithium storage coating may be described as amatrix of interconnected silicon, germanium or alloys thereof, withrandom pores and interstices embedded therein. In some embodiments, thelithium storage coating has a sponge-like form. In some embodiments,about 75% or more of the metal oxide coating surface is contiguous withthe lithium storage coating, at least prior to electrochemicalformation. It should be noted that the lithium storage coating does notnecessarily extend across the entire anode without any lateral breaksand may include random discontinuities or cracks and still be consideredcontinuous.

In some embodiments, the lithium storage coating includes asubstoichiometric oxide of silicon (SiO_(x)), germanium (GeO_(x)) or tin(SnO_(x)) wherein the ratio of oxygen atoms to silicon, germanium or tinatoms is less than 2:1, i.e., x<2, alternatively less than 1:1, i.e.,x<1. In some embodiments, x is in a range of 0.02 to 0.95, alternatively0.02 to 0.10, alternatively 0.10 to 0.50, or alternatively 0.50 to 0.95,alternatively 0.95 to 1.25, alternatively 1.25 to 1.50, or anycombination of contiguous ranges thereof.

In some embodiments, the lithium storage coating includes asubstoichiometric nitride of silicon (SiN_(y)), germanium (GeN_(y)) ortin (SnN_(y)) wherein the ratio of nitrogen atoms to silicon, germaniumor tin atoms is less than 1.25:1, i.e., y <1.25. In some embodiments, yis in a range of 0.02 to 0.95, alternatively 0.02 to 0.10, alternatively0.10 to 0.50, or alternatively 0.50 to 0.95, alternatively 0.95 to 1.20,or any combination of contiguous ranges thereof.

In some embodiments, the lithium storage coating includes asubstoichiometric oxynitride of silicon (SiO_(x)N_(y)), germanium(GeO_(x)N_(y)), or tin (SnO_(x)N_(y)) wherein the ratio of total oxygenand nitrogen atoms to silicon, germanium or tin atoms is less than 1:1,i.e., (x+y)<1. In some embodiments, (x+y) is in a range of 0.02 to 0.95,alternatively 0.02 to 0.10, alternatively 0.10 to 0.50, or alternatively0.50 to 0.95, or any combination of contiguous ranges thereof.

In some embodiments, the above sub-stoichiometric oxides, nitrides oroxynitrides are provided by a CVD process, including but not limited to,a PECVD process. The oxygen and nitrogen may be provided uniformlywithin the lithium storage coating, or alternatively the oxygen ornitrogen content may be varied as a function of storage layer thickness.

In some embodiments, a lithium storage coating may include two or moresublayers, optionally continuous and/or porous lithium storagesublayers, having different compositions. In some embodiments, thelithium storage coating, optionally a continuous and/or porous lithiumstorage coating, includes a gradient of components, density, orporosity, or a combination thereof.

Additional Lithium Storage Materials

In some embodiments, conventional lithium-ion battery slurries based oncarbon that may optionally further include silicon particles, may becoated over anodes of the present disclosure to further enhance chargecapacity. Coating methods may include curtain coating, slot coating,spin coating, inkjet, coating, spray coating, or any other suitablemethod.

CVD

CVD generally involves flowing a precursor gas, a gasified liquid interms of direct liquid injection CVD or gases and liquids into a chambercontaining one or more objects, typically heated, to be coated. Chemicalreactions occur on and near the hot surfaces, resulting in thedeposition of a thin film on the surface. This is accompanied by theproduction of chemical by-products that are exhausted out of the chamberalong with unreacted precursor gases. As would be expected with thelarge variety of materials deposited and the wide range of applications,there are many variants of CVD that may be used to form the lithiumstorage coating, the metal oxide coating, a supplemental layer (seebelow) or other layer. It may be done in hot-wall reactors or cold-wallreactors, at sub-torr total pressures to above-atmospheric pressures,with and without carrier gases, and at temperatures typically rangingfrom 100-1600° C. in some embodiments. There are also a variety ofenhanced CVD processes, which involve the use of plasmas, ions, photons,lasers, hot filaments, or combustion reactions to increase depositionrates and/or lower deposition temperatures. Various process conditionsmay be used to control the deposition, including but not limited to,temperature, precursor material, gas flow rate, pressure, substratevoltage bias (if applicable), and plasma energy (if applicable).

As mentioned, the lithium storage coating, e.g., a layer of silicon orgermanium or both, may be provided by plasma-enhanced chemical vapordeposition (PECVD). Relative to conventional CVD, deposition by PECVDcan often be done at lower temperatures and higher rates, which can beadvantageous for higher manufacturing throughput. In some embodiments,the PECVD is used to deposit a substantially amorphous silicon layer(optionally doped) over the metal oxide coating. In some embodiments,PECVD is used to deposit a substantially amorphous porous siliconcoating over the metal oxide coating.

PECVD

In PECVD processes, according to various implementations, a plasma maybe generated in a chamber in which the substrate is disposed or upstreamof the chamber and fed into the chamber. Various types of plasmas may beused including, but not limited to, capacitively- coupled plasmas,inductively-coupled plasmas, and conductive coupled plasmas. Anyappropriate plasma source may be used, including DC, AC, RF, VHF,combinatorial PECVD and microwave sources may be used. Some non-limitingexamples of useful PECVD tools include hollow cathode tube PECVD,magnetron confined PECVD, inductively coupled plasma chemical vapordeposition (ICP-PECVD, sometimes called HDPECVD, ICP-CVD or HDCVD), andexpanding thermal plasma chemical vapor deposition (ETP-PECVD).

PECVD process conditions (temperatures, pressures, precursor gases,carrier gasses, dopant gases, flow rates, energies, and the like) canvary according to the particular process and tool used, as is well knownin the art.

In some implementations, the PECVD process is an expanding thermalplasma chemical vapor deposition (ETP-PECVD) process. In such a process,a plasma generating gas is passed through a direct current arc plasmagenerator to form a plasma, with a web or other substrate including thecurrent collector optionally in an adjoining vacuum chamber. A siliconsource gas is injected into the plasma, with radicals generated. Theplasma is expanded via a diverging nozzle and injected into the vacuumchamber and toward the substrate. An example of a plasma generating gasis argon (Ar). In some embodiments, the ionized argon species in theplasma collide with silicon source molecules to form radical species ofthe silicon source, resulting in deposition onto the current collector.Example ranges for voltages and currents for the DC plasma source are 60to 80 volts and 40 to 70 amperes, respectively.

Any appropriate silicon source may be used to deposit silicon, includingsilane (SiH₄), dichlorosilane (H₂SiCl₂), monochlorosilane (H₃SiCl),trichlorosilane (HSiCl₃), silicon tetrachloride (SiCl₄), anddiethylsilane. Depending on the gas(es) used, the silicon layer may beformed by decomposition or reaction with another compound, such as byhydrogen reduction. In some embodiments, the gases may include a siliconsource such as silane, a noble gas such as helium, argon, neon, orxenon, optionally one or more dopant gases, and substantially nohydrogen. In some embodiments, the gases may include argon, silane, andhydrogen, and optionally some dopant gases. In some embodiments the gasflow ratio of argon relative to the combined gas flows for silane andhydrogen is at least 3.0, alternatively at least 4.0. In someembodiments, the gas flow ratio of argon relative to the combined gasflows for silane and hydrogen is in a range of 3-5, alternatively 5-10,alternatively 10-15, alternatively 15-20, or any combination ofcontiguous ranges thereof. In some embodiments, the gas flow ratio ofhydrogen gas to silane gas is in a range of 0-0.1, alternatively0.1-0.2, alternatively 0.2-0.5, alternatively 0.5-1, alternatively 1-2,alternatively 2-5, or any combination of contiguous ranges thereof. Insome embodiments, higher porosity silicon may be formed and/or the rateof silicon deposition may be increased when the gas flow ratio of silanerelative to the combined gas flows of silane and hydrogen increases. Insome embodiments a dopant gas is borane or phosphine, which may beoptionally mixed with a carrier gas. In some embodiments, the gas flowratio of dopant gas (e.g., borane or phosphine) to silicon source gas(e.g., silane) is in a range of 0.0001-0.0002, alternatively0.0002-0.0005, alternatively 0.0005-0.001, alternatively 0.001-0.002,alternatively 0.002-0.005, alternatively 0.005-0.01, alternatively0.01-0.02, alternatively 0.02-0.05, alternatively 0.05-0.10, or anycombination of contiguous ranges thereof. Such gas flow ratios describedabove may refer to the relative gas flow, e.g., in standard cubiccentimeter per minute (SCCM). In some embodiments, the PECVD depositionconditions and gases may be changed over the course of the deposition.

In some embodiments, the temperature at the current collector during atleast a portion of the time of PECVD deposition is in a range of 100° C.to 200° C., alternatively 200° C. to 300° C., alternatively 300° C. to400° C., alternatively 400° C. to 500° C., alternatively 500° C. to 600°C., or any combination of contiguous ranges thereof. In someembodiments, the temperature may vary during the time of PECVDdeposition. For example, the temperature during early times of the PECVDmay be higher than at later times. Alternatively, the temperature duringlater times of the PECVD may be higher than at earlier times.

The thickness or mass per unit area of the lithium storage coatingdepends on the storage material, desired charge capacity and otheroperational and lifetime considerations. Increasing the thicknesstypically provides more capacity. If the lithium storage coating becomestoo thick, electrical resistance may increase and the stability maydecrease. In some embodiments, the anode may be characterized as havingan active silicon areal density of at least 0.5 mg/cm², alternatively atleast 1.0 mg/cm², alternatively at least 1.5 mg/cm², alternatively atleast 3mg/cm², alternatively at least 5 mg/cm². In some embodiments, thelithium storage structure may be characterized as having an activesilicon areal density in a range of 0.5-1.5 mg/cm², alternatively 1.5-2mg/cm², alternatively in a range of 2-3 mg/cm², alternatively in a rangeof 3-5 mg/cm², alternatively in a range of 5-10 mg/cm², alternatively ina range of 10-15 mg/cm², alternatively in a range of 15-20 mg/cm², orany combination of contiguous ranges thereof. “Active areal silicondensity” refers to the silicon in electrical communication with thecurrent collector that is available for reversible lithium storage atthe beginning of cell cycling, e.g., after anode “electrochemicalformation” discussed later. “Areal” of this term refers to the totalsurface area of the electrically conductive substrate (including areaoccupied by the electrically conductive structures, excluding thesurface area of the electrically conductive structures themselves). Insome embodiments, not all of the silicon content is active silicon,i.e., some may be tied up in the form of non-active silicides orelectrically isolated from the current collector.

The lithium storage coating may be characterized as having a thicknessthat may be measured from an outer surface of the lithium storagecoating to the nearest metal oxide material. In some embodiments, thethickness of the lithium storage coating varies as a function oflocation on the current collector. In some embodiments the lithiumstorage coating has an average thickness of at least 0.5 μm,alternatively ate least 1μm, alternatively at least 3μm, alternativelyat least 7μm. In some embodiments, the lithium storage coating has anaverage thickness in a range of about 0.5 μm to about 50 μm. In someembodiments, the lithium storage coating comprises at least 85 atomic %amorphous silicon and has a thickness in a range of 0.5 to 1 μm,alternatively 1-2 μm, alternatively 2-4 μm, alternatively 4-7 μm,alternatively 7-10 μm, alternatively 10-15 μm , alternatively 15-20 μm,alternatively 20-25 μm, alternatively 25-30 μm, alternatively 30-40 μm,alternatively 40-50 μm, or any combination of contiguous ranges thereof.

In some embodiments, the lithium storage coating includes silicon butdoes not contain a substantial amount of crystalline silicides, i.e.,the presence of silicides is not readily detected by X-Ray Diffraction(XRD). Metal silicides, e.g., nickel silicide, commonly form whensilicon is deposited at higher temperatures directly onto metal, e.g.,nickel foil. Metal silicides such as nickel silicides often have muchlower lithium storage capacity than silicon itself. In some embodiments,the average atomic % of silicide-forming metallic elements within thelithium storage coating are on average less than 35%, alternatively lessthan 20%, alternatively less than 10%, alternatively less than 5%. Insome embodiments, the average atomic % of silicide-forming metallicelements within the lithium storage coating are in a range of about0.01% to about 10%, alternatively about 0.05 to about 5%. In someembodiments, the atomic % of silicide forming metallic elements in thelithium storage coating is higher nearer the current collector than awayfrom the current collector.

Other Anode Features

In some embodiments, the anode may further include one or moresupplemental layers. provided over the outer surface of the lithiumstorage coating. In some embodiments, the supplemental layer is aprotection layer to enhance lifetime or physical durability. Thesupplemental layer may be an oxide or nitride formed from the lithiumstorage material itself, e.g., silicon dioxide, silicon nitride, orsilicon oxynitride in the case of silicon. A supplemental layer may bedeposited, for example, by ALD, CVD, PECVD, evaporation, sputtering,solution coating, ink jet or any method that is compatible with theanode. In some embodiments, a supplemental layer is deposited in thesame CVD or PECVD device as the lithium storage coating. For example,stoichiometric silicon dioxide or silicon nitride supplemental layer bybe formed by introducing an oxygen- or nitrogen-containing gas (or both)along with the silicon precursor gas used to form the lithium storagecoating. In some embodiments the supplemental layer may include boronnitride or silicon carbide. In some embodiments, a supplemental layermay include a metal compound as described below.

In some embodiments, the one or more supplemental layers may helpstabilize the lithium storage coating by providing a barrier to directelectrochemical reactions with solvents or electrolytes that can degradethe interface. A supplemental layer should be reasonably conductive tolithium ions and permit lithium ions to move into and out of the lithiumstorage coating during charging and discharging. In some embodiments,the lithium ion conductivity of a supplemental layer is at least 10⁻⁹S/cm, alternatively at least 10⁻⁸ S/cm, alternatively at least 10⁻⁷S/cm, alternatively at least 10⁻⁶ S/cm. In some embodiments, thesupplemental layer acts as a solid-state electrolyte. In someembodiments, the supplemental layer(s) are less electrically conductivethan the lithium storage structure so that little or no electrochemicalreduction of lithium ions to lithium metal occurs at the supplementallayer/electrolyte interface. In addition to providing protection fromelectrochemical reactions, a multiple supplemental layer structureembodiments may provide superior structural support. In someembodiments, although the supplemental layers may flex and may formfissures when the lithium storage coating expands during lithiation,crack propagation can be distributed between the layers to reduce directexposure of the lithium storage structure to the bulk electrolyte. Forexample, a fissure in the second supplemental layer may not align with afissure in the first supplemental layer. Such an advantage may not occurif just one thick supplemental layer is used. In an embodiment, thesecond supplemental layer may be formed of a material having higherflexibility than the first supplemental layer.

In some embodiments, a supplemental layer may include silicon nitride,e.g., substantially stoichiometric silicon nitride where the ratio ofnitrogen to silicon is in a range of 1.33 to 1.25. A supplemental layercomprising silicon nitride may have an average thickness in a range ofabout 0.5 nm to 1 nm, alternatively 1 nm to 2 nm, alternatively 2 nm to10 nm, alternatively 10 nm to 20 nm, alternatively 20 nm to 30 nm,alternatively 30 nm to 40 nm, alternatively 40 nm to 50 nm, or anycombination of contiguous ranges thereof. Silicon nitride may bedeposited by an atomic layer deposition (ALD) process or by a CVDprocess. In some embodiments, the lithium storage coating includessilicon deposited by some type of CVD process as described above, and atthe end, a nitrogen gas source is added to the CVD deposition chamberalong with the silicon source.

In some embodiments, a supplemental layer may include silicon dioxide,e.g., substantially stoichiometric silicon dioxide where the ratio ofoxygen to silicon is in a range of 2.0 to 1.9. A supplemental layercomprising silicon dioxide may have an average thickness in a range ofabout 2 nm to 10 nm, alternatively 10 nm to 30 nm, alternatively 30 nmto 50 nm, alternatively 50 nm to 70 nm, alternatively 70 nm to 100 nm,alternatively 100 nm to 150 nm, alternatively 150 nm to 200 nm, or anycombination of contiguous ranges thereof. Silicon dioxide may bedeposited by an atomic layer deposition (ALD) process or by a CVDprocess. In some embodiments, the lithium storage coating includessilicon deposited by some type of CVD process as described above, and atthe end, an oxygen-containing gas source is added to the CVD depositionchamber along with the silicon source.

In some embodiments, a supplemental layer may include siliconoxynitride, e.g., a substantially stoichiometric oxynitride of silicon(SiO_(x)N_(y)) wherein the sum of 0.5x and 0.75y is in a range of 1.00to 0.95. A supplemental layer comprising silicon nitride may have anaverage thickness in a range of about 0.5 nm to 1 nm, alternatively 1 nmto 2 nm, alternatively 2 nm to 10 nm, alternatively 10 nm to 20 nm,alternatively 20 nm to 30 nm, alternatively 30 nm to 40 nm,alternatively 40 nm to 50 nm, alternatively 50 nm to 70 nm,alternatively 70 nm to 100 nm, alternatively 100 nm to 150 nm, or anycombination of contiguous ranges thereof. In some embodiments, siliconoxynitride may be provided by a CVD process, including but not limitedto, a PECVD process. The oxygen and nitrogen may be provided uniformlywithin the lithium storage coating, or alternatively the oxygen ornitrogen content may be varied as a function of position (e.g., height)within the storage layer.

In some embodiments, silicon nitride, silicon dioxide, or siliconoxynitride may be deposited by an atomic layer deposition (ALD) processor by a CVD process. In some embodiments, the lithium storage coatingincludes silicon deposited by some type of CVD process as describedabove, and at the end, a nitrogen- and/or an oxygen-containing gassource is added to the CVD deposition chamber along with the siliconsource.

In some embodiments a supplemental layer may include a metal compound.In some embodiments, the metal compound includes a metal oxide, metalnitride, or metal oxynitride, e.g., those containing aluminum, titanium,vanadium, zirconium, or tin, or mixtures thereof. In some embodiments, asupplemental layer including a metal oxide, metal nitride, or metaloxynitride, may have an average thickness of less than about 100 nm, forexample, in a range of about 0.5 nm to about 1 nm, alternatively about 1nm to about 2 nm, alternatively 2 nm to 10 nm, alternatively 10 nm to 20nm, alternatively 20 nm to 30 nm, alternatively 30 nm to 40 nm,alternatively 40 nm to 50 nm, or any combination of contiguous rangesthereof. The metal oxide, metal nitride, or metal oxynitride may includeother components or dopants such as transition metals, phosphorous orsilicon.

In some embodiments, the metal compound may include a lithium-containingmaterial such as lithium phosphorous oxynitride (LIPON), a lithiumphosphate, a lithium aluminum oxide, or a lithium lanthanum titanate. Insome embodiments, the thickness of supplemental layer including alithium-containing material may be in a range of 0.5 nm to 200 nm,alternatively 1 nm to 10 nm, alternatively 10 nm to 20 nm, alternatively20 nm to 30 nm, alternatively 30 nm to 40 nm, alternatively 40 nm to 50nm, alternatively 50 nm to 100 nm, alternatively 100 to 200 nm, or anycombination of contiguous ranges thereof.

In some embodiments the metal compound may be deposited by a processcomprising ALD, thermal evaporation, sputtering, or e-beam evaporation.ALD is a thin-film deposition technique typically based on thesequential use of a gas phase chemical process. The majority of ALDreactions use at least two chemicals, typically referred to asprecursors. These precursors react with the surface of a material one ata time in a sequential, self-limiting, manner. Through the repeatedexposure to separate precursors, a thin film is deposited, often in aconformal manner. In addition to conventional ALD systems, so-calledspatial ALD (SALD) methods and materials can be used, e.g., as describedU.S. Pat. No. 7,413,982, the entire contents of which are incorporatedby reference herein for all purposes. In certain embodiments, SALD canbe performed under ambient conditions and pressures and have higherthroughput than conventional ALD systems.

In some embodiments, the process for depositing the metal compound mayinclude electroless deposition, contact with a solution, contact with areactive gas, or electrochemical methods. In some embodiments, a metalcompound may be formed by depositing a metallic layer (including but notlimited to thermal evaporation, CVD, sputtering, e-beam evaporation,electrochemical deposition, or electroless deposition) followed bytreatment to convert the metal to the metal compound (including but notlimited to, contact with a reactive solution, contact with an oxidizingagent, contact with a reactive gas, or a thermal treatment).

The supplemental layer may include an inorganic-organic hybrid structurehaving alternating layers of metal oxide and bridging organic materials.These inorganic-organic hybrid structures are sometimes referred to as“metalcone”. Such structures can be made using a combination of atomiclayer deposition to apply the metal compound and molecular layerdeposition (MLD) to apply the organic. The organic bridge is typically amolecule having multiple functional groups. One group can react with alayer comprising a metal compound and the other group is available toreact in a subsequent ALD step to bind a new metal. There is a widerange of reactive organic functional groups that can be used including,but not limited to hydroxy, carboxylic acid, amines, acid chlorides andanhydrides. Almost any metal compound suitable for ALD deposition can beused. Some non-limiting examples include ALD compounds for aluminum(e.g., trimethyl aluminum), titanium (e.g., titanium tetrachloride),zinc (e.g., diethyl zinc), and zirconium(tris(dimethylamino)cyclopentadienyl zirconium). For the purposes of thepresent disclosure, this alternating sublayer structure of metaloxide/bridging organic is considered a single supplemental layer ofmetalcone. When the metal compound includes aluminum, such structuresmay be referred to as an alucone. Similarly, when the metal compoundincludes zirconium, such structures may be referred to as a zircone.Further examples of inorganic-organic hybrid structures that may besuitable as a supplemental layer may be found in U.S. Pat. No.9,376,455, and US patent publications 2019/0044151 and 2015/0072119, theentire contents of which are incorporated herein by reference.

In some embodiments, a supplemental layer having a metalcone may have athickness in a range of 0.5 nm to 200 nm, alternatively 1 nm to 10 nm,alternatively 10 nm to 20 nm, alternatively 20 nm to 30 nm,alternatively 30 nm to 40 nm, alternatively 40 nm to 50 nm,alternatively 50 nm to 100 nm, alternatively 100 to 200 nm, or anycombination of contiguous ranges thereof.

In some embodiments a supplemental layer (a first, a second, or anadditional supplemental layer) may include boron nitride or siliconcarbide and may have an average thickness of less than about 100 nm, forexample, in a range of about 0.5 nm to about 1 nm, alternatively about 1nm to about 2 nm, alternatively 2 nm to 10 nm, alternatively 10 nm to 20nm, alternatively 20 nm to 30 nm, alternatively 30 nm to 40 nm,alternatively 40 nm to 50 nm, or any combination of contiguous rangesthereof.

In some embodiments the anode is at least partially pre-lithiated, i.e.,the lithium storage coating and/or a metal oxide coating includes somelithium prior to battery assembly, that is, prior to combining the anodewith a cathode in a battery cell. Note that “lithiated storage coating”simply means that at least some of the potential storage capacity of thelithium storage coating is filled, but not necessarily all. In someembodiments, the lithiated storage coating may include lithium in arange of 1% to 10% of the theoretical lithium storage capacity of thelithium storage coating, alternatively 10% to 20%, alternatively, 20% to30%, alternatively 30% to 40%, alternatively 40% to 50%, alternatively50% to 60%, alternatively 60% to 70%, alternatively 70% to 80%,alternatively 80% to 90%, alternatively 90% to 100%, or any combinationof contiguous ranges thereof. In some embodiments, the metal oxidecoating may capture some of the lithium, and one may need to account forsuch capture to achieve the desired lithium range in the lithiatedstorage coating.

In some embodiments prelithiation may include depositing lithium metalover the lithium storage coating, e.g., by evaporation, e-beam orsputtering. Alternatively, prelithiation may include contacting theanode with a reductive lithium organic compound, e.g., lithiumnaphthalene, n-butyllithium or the like. In some embodiments,prelithiation may include incorporating lithium by electrochemicalreduction of lithium ion in prelithiation solution.

In some embodiments, prelithiation includes physical contact of thelithium storage coating with a lithiation material. The lithiationmaterial may include a reducing lithium compound, lithium metal or astabilized lithium metal powder, any of which may optionally be providedas a coating on a lithium transfer substrate. The lithium transfersubstrate may include a metal (e.g., as a foil), a polymer, a ceramic,or some combination of such materials, optionally in a multilayerformat. In some embodiments, such lithiation material may be provided onat least one side of a current separator that faces the anode, i.e., thecurrent separator also acts as a lithium transfer substrate. Stabilizedlithium metal powders (“SLMP”) typically have a phosphate, carbonate orother coating over the lithium metal particles, e.g. as described inU.S. Pat. Nos. 8,377,236, 6,911,280, 5,567,474, 5,776,369, and5,976,403, the entire contents of which are incorporated herein byreference. In some embodiments SLMPs may require physical pressure tobreak the coating and allow incorporation of the lithium into thelithium storage coating. In some embodiments, other lithiation materialsmay be applied with pressure and/or heat to promote lithium transferinto the lithium storage coating, optionally through one or moresupplemental layers. In some embodiments a pressure applied between ananode and a lithiation material may be at least 200 kPa, alternativelyat least 1000 kPa, alternatively at least 5000 kPa. Pressure may beapplied, for example, by calendering, pressurized plates, or in the caseof a lithiation material coating on a current separator, by assemblyinto battery having confinement or other pressurizing features.

In some embodiments, prelithiation includes thermally treating thelithium storage coating during lithium incorporation, after lithiumincorporation, or both during and after. The thermal treatment mayassist in the incorporation of the lithium into the lithium storagecoating, for example by promoting lithium diffusion. In someembodiments, thermally treating includes exposing the anode to atemperature in a range of 50° C. to 100° C., alternatively 100° C. to150° C., alternatively 150° C. to 200° C., alternatively 200° C. to 250°C., alternatively 250° C. to 300° C., or alternatively 300° C. to 350°C. In some embodiments, thermal treatment may be done under controlledatmosphere, e.g., under vacuum or argon atmosphere to avoid unwantedreactions with oxygen, nitrogen, water or other reactive gases.

In some embodiments, prelithiation may soften the lithium storagecoating, for example, due to the formation of a lithium-silicon alloy.This softening may cause problems in some processes, for example,roll-to-roll processes whereby the softened lithium storage coatingbegins to stick to rollers or to itself during winding. In someembodiments providing at one or more supplemental layers prior toprelithiation or after prelithiation, the structural integrity andprocessability of the anode may be substantially improved. In someembodiments, the supplemental layer(s) may act as a harder interfacewith other surfaces to prevent or reduce contact of such surfaces withthe softened lithium storage material.

In some embodiments, lithium metal may be deposited over the lithiumstorage coating followed by deposition of lithium ion-conducting layer.The anode may be thermally treated prior to deposition of the lithiumion-conducting layer, after deposition of the lithium ion-conductinglayer, or both. In some embodiments, the lithium metal is depositeddirectly onto the lithium storage coating. In some embodiments, asupplemental layer, e.g., silicon nitride, is deposited onto the lithiumstorage coating prior to deposition of the lithium metal. In someembodiments, the lithium ion-conducting layer may include alithium-containing material, a metal oxide, or a metalcone. Somenon-limiting examples of lithium ion-conducting layer materials includea lithium phosphorous oxynitride (LIPON), a lithium phosphate, a lithiumaluminum oxide, a lithium lanthanum titanate, and alucones. The lithiumion-conducting layer may include multiple sublayers of differentmaterials, e.g., selected from the above list.

Thermal treatments were discussed above with respect to prelithiationand metal oxide precursors, but in some embodiments the anode may bethermally treated prior to battery assembly (after deposition of thelithium storage coating is complete, but before the anode is combinedwith a cathode in a battery cell), with or without a prelithiation step.In some embodiments, thermally treating the anode may improve adhesionof the various layers or electrical conductivity, e.g., by inducingmigration of metal from the current collector (i.e., the metal oxidecoating or the underlying first or second electrically conductivematerials) or atoms from the optional supplemental layer into thelithium storage coating. In some embodiments, thermally treating theanode may be done in a controlled environment, e.g., under vacuum,argon, or nitrogen having a low oxygen and water content (e.g., lessthan 100 ppm or partial pressure of less than 10 Torr, alternativelyless than 1 Torr, alternatively less than 0.1 Torr to preventdegradation). Herein, “under vacuum” generally refers to a reducedpressure condition wherein the total pressure of all gasses (e.g. in avacuum oven) is less than 10 Torr. Due to equipment limitations, thevacuum pressure is typically greater than about 10⁻⁸ Torr. In someembodiments, anode thermal treatment may be carried out using an oven, atube furnace, infrared heating elements, contact with a hot surface(e.g. a hot plate), or exposure to a flash lamp. The anode thermaltreatment temperature and time depend on the materials of the anode. Insome embodiments, anode thermal treatment includes heating the anode toa temperature of at least 50° C., optionally in a range of 50° C. to600° C., alternatively 100° C. to 250° C., alternatively 250° C. to 350°C., alternatively 350° C. to 450° C., alternatively 450° C. to 600° C.,alternatively 600° C. to 700° C., alternatively 700° C. to 800° C., orany combination of contiguous ranges thereof. In some embodiments, theanode thermal treatment time may be in a range of about 0.1 min to about1 min, alternatively about 1 min to about 5 mins, alternatively about 5mins to about 10 mins, alternatively about 10 mins to about 30 minutes,alternatively about 30 mins to about 60 mins, alternatively about 60mins to about 90 mins, alternatively in a range of about 90 mins toabout 120 mins, or any combination of contiguous ranges thereof.

In some embodiments one or more of the above processing steps may beperformed using roll-to-roll coating methods wherein the electricallyconductive substrate is in the form of a rolled film.

Battery Features

The preceding description relates primarily to the anode (negativeelectrode) of a lithium-ion battery (LIB). The LIB typically includes acathode (positive electrode), an electrolyte and a separator (if notusing a solid-state electrolyte). As is well known, batteries can beformed into multilayer stacks of anodes and cathodes with an interveningseparator. Alternatively, a single anode/cathode stack can be formedinto a so-called jellyroll. Such structures are provided into anappropriate housing having desired electrical contacts.

In some embodiments, the battery may be constructed with confinementfeatures to limit expansion of the battery, e.g., as described in USpublished applications 2018/0145367 and 2018/0166735, the entirecontents of which are incorporated herein by reference for all purposes.In some embodiments a physical pressure is applied between the anode andcathode, e.g., using a tensioned spring or clip, a compressible film orthe like. Confinement, pressure, or both confinement and pressure mayhelp ensure that the anode remains in active contact with the currentcollector during formation and cycling, which may cause expansion andcontraction of the lithium storage coating. In some embodiments, ajelly-roll battery design using metallic or other hard cylindricalhousings may provide effective confinement, pressure, or bothconfinement and pressure.

FIG. 8 is a schematic cross-sectional view of a battery according tosome embodiments of the present disclosure. Battery 1090 includes topplate 1060, bottom plate 1062, anode side plate 1064, and cathode sideplate 1066, which form part of a housing for the stack of anodes 1000,cathodes 1040, and intervening separators 1030. Anodes 1000 may includeany anode described herein. Anodes are attached to an anode bus 1020which is connected to anode lead 1022 that extends through anode sideplate 1064. Cathodes are attached to a cathode bus 1050 which isconnected to cathode lead 1052 that extends through cathode side plate1066. Battery 1090 further includes electrolyte 1080 which fills thespace and saturates the separators 1030. Top compression member 1070 andlower compression member 1072 apply physical pressure (arrows) betweenthe anodes and cathodes. Compression members may be compressible films,e.g., made from a porous polymer or silicone. Alternatively, compressionmembers may include an array of compressible features, e.g., made fromporous polymer or silicone. Alternatively, the compression members mayinclude springs or an array of springs. Alternatively, compressionmembers may correspond to two sides of a compression clip or clamp. Insome embodiments, the separator may act as a compressible film. In someembodiments the top and bottom plates may be formed a material and/orstructured to resist deformation thereby confining battery swell.

Cathode

Positive electrode (cathode) materials include, but are not limited to,lithium metal oxides or compounds (e.g., LiCoO₂, LiFePO₄, LiMnO₂,LiNiO₂, LiMn₂O₄, LiCoPO₄, LiNi_(x)Co_(y)Mn_(z)O₂,LiNi_(X)Co_(Y)Al_(Z)O₂, LiFe₂(SO₄)₃, or Li₂FeSiO₄), carbon fluoride,metal fluorides such as iron fluoride (FeF₃), metal oxide, sulfur,selenium, sulfur-selenium and combinations thereof. Cathode activematerials are typically provided on, or in electrical communicationwith, an electrically conductive cathode current collector.

In some embodiments, a prelithiated anode of the present disclosure isused with cathode including sulfur, selenium, or both sulfur andselenium (collectively referred to herein as “chalcogen cathodes”). Insome embodiments, a prelithiated anode of the present disclosure may bepaired with a chalcogen cathode having an active material layer, whereinthe active material layer may include a carbon material and a compoundselected selected from the group consisting of Se, Se_(y)S_(x),Te_(y)S_(x), Te_(z)Se_(y)S_(x), and combinations thereof, where x, y andz are any value between 0 and 1, the sum of y and x being 1, and the sumof z, y and x being 1, the compound impregnated in the carbon material ,e.g., as described in US published application 2019/0097275, which isincorporated by reference herein for all purposes. The compound may bepresent in an amount of 9-90% by weight based on the total weight of theactive material layer. In some embodiments, the chalcogen cathode activematerial layer further includes conductive carbon nanotubes to improveoverall conductivity and physical durability and may permit fastercharging and discharging. The presence of carbon nanotubes may furtherallow thicker coatings that have greater flexibility thereby allowinghigher capacity.

Chalcogen cathodes are generally paired with lithium metal anodes.However, lithium metal anodes are difficult to handle, prone todegradation, and may further allow formation of dangerous dendriticlithium that can lead to catastrophic shorts. In some embodiments,prelithiated anodes of the present disclosure can achieve equivalentenergy storage capacity of a pure lithium anode, but are much easier tohandle and less prone to form dendritic lithium, thus making them morecompatible with chalcogen cathodes.

Current Separator

The current separator allows ions to flow between the anode and cathodebut prevents direct electrical contact. Such separators are typicallyporous sheets. Non-aqueous lithium-ion separators are single layer ormultilayer polymer sheets, typically made of polyolefins, especially forsmall batteries. Most commonly, these are based on polyethylene orpolypropylene, but polyethylene terephthalate (PET) and polyvinylidenefluoride (PVDF) can also be used. For example, a separator can have >30%porosity, low ionic resistivity, a thickness of ˜10 to 50 μm and highbulk puncture strengths. Separators may alternatively include glassmaterials, ceramic materials, a ceramic material embedded in a polymer,a polymer coated with a ceramic, or some other composite or multilayerstructure, e.g., to provide higher mechanical and thermal stability. Asmentioned, the separator may include a lithiation material such aslithium metal, a reducing lithium compound, or an SLMP material coatedat least on the side facing the anode.

Electrolyte

The electrolyte in lithium ion cells may be a liquid, a solid, or a gel.A typical liquid electrolyte comprises one or more solvents and one ormore salts, at least one of which includes lithium. During the first fewcharge cycles (sometimes referred to as formation cycles), the organicsolvent and/or the electrolyte may partially decompose on the negativeelectrode surface to form an SEI (Solid-Electrolyte-Interphase) layer.The SEI is generally electrically insulating but ionically conductive,thereby allowing lithium ions to pass through. The SEI may lessendecomposition of the electrolyte in the later charging cycles.

Some non-limiting examples of non-aqueous solvents suitable for somelithium ion cells include the following: cyclic carbonates (e.g.,ethylene carbonate (EC), fluoroethylene carbonate (FEC), propylenecarbonate (PC), butylene carbonate (BC) and vinylethylene carbonate(VEC)), vinylene carbonate (VC), lactones (e.g., gamma-butyrolactone(GBL), gamma-valerolactone (GVL) and alpha-angelica lactone (AGL)),linear carbonates (e.g., dimethyl carbonate (DMC), methyl ethylcarbonate (MEC, also commonly abbreviated EMC), diethyl carbonate (DEC),methyl propyl carbonate (MPC), dipropyl carbonate (DPC), methyl butylcarbonate (NBC) and dibutyl carbonate (DBC)), ethers (e.g.,tetrahydrofuran (THF), 2-methyltetrahydrofuran, 1,4-dioxane,1,2-dimethoxyethane (DME), 1,2-diethoxyethane and 1,2-dibutoxyethane),nitriles (e.g., acetonitrile and adiponitrile) linear esters (e.g.,methyl propionate, methyl pivalate, butyl pivalate and octyl pivalate),amides (e.g., dimethyl formamide), organic phosphates (e.g., trimethylphosphate and trioctyl phosphate), organic compounds containing an S═Ogroup (e.g., dimethyl sulfone and divinyl sulfone), and combinationsthereof.

Non-aqueous liquid solvents can be employed in combination. Examples ofthese combinations include combinations of cyclic carbonate-linearcarbonate, cyclic carbonate-lactone, cyclic carbonate-lactone-linearcarbonate, cyclic carbonate-linear carbonate-lactone, cycliccarbonate-linear carbonate-ether, and cyclic carbonate-linearcarbonate-linear ester. In some embodiments, a cyclic carbonate may becombined with a linear ester. Moreover, a cyclic carbonate may becombined with a lactone and a linear ester. In some embodiments, theweight ratio, or alternatively the volume ratio, of a cyclic carbonateto a linear ester is in a range of 1:9 to 10:1, alternatively 2:8 to 7:3

A salt for liquid electrolytes may include one or more of the followingnon-limiting examples: LiPF₆, LiBF₄, LiClO₄, LiAsF₆, LiN(CF₃SO₂)₂,LiN(C₂F₅SO₂)₂, LiCF₃SO₃, LiC(CF₃SO₂)₃, LiPF₄(CF₃)₂, LiPF₃(C₂F₅)₃,LiPF₃(CF₃)₃, LiPF₃ (iso-C₃F₇)₃, LiPF₅(iso-C₃F₇), lithium salts havingcyclic alkyl groups (e.g., (CF₂)₂(SO₂)_(2x)Li and (CF₂)₃(SO₂)_(2x)Li),and combinations thereof. Common combinations include: LiPF₆ and LiBF₄;LiPF₆ and LiN(CF₃SO₂)₂; and LiBF₄ and LiN(CF₃SO₂)₂.

In some embodiments, the total concentration of salt in a liquidnon-aqueous solvent (or combination of solvents) is at least 0.3 M,alternatively at least 0.7M. The upper concentration limit may be drivenby a solubility limit and operational temperature range. In someembodiments, the concentration of salt is no greater than about 2.5 M,alternatively no more than about 1.5 M.

In some embodiments, the battery electrolyte includes a non-aqueousionic liquid and a lithium salt.

A solid-state electrolyte may be used without the separator because itserves as the separator itself. It is electrically insulating, ionicallyconductive, and electrochemically stable. In some embodiments, asolid-state electrolyte may be vapor deposited, solution-coated,melt-coated or a combination thereof. In the solid electrolyteconfiguration, a lithium containing salt, which could be the same as forthe liquid electrolyte cells described above, is employed but ratherthan being dissolved in an organic solvent, it is held in a solidpolymer composite. Examples of solid polymer electrolytes may beionically conductive polymers prepared from monomers containing atomshaving lone pairs of electrons available for the lithium ions ofelectrolyte salts to attach to and move between during conduction, suchas polyvinylidene fluoride (PVDF) or chloride or copolymer of theirderivatives, poly(chlorotrifluoroethylene),poly(ethylene-chlorotrifluoro-ethylene), or poly(fluorinatedethylene-propylene), polyethylene oxide (PEO) and oxymethylene linkedPEO, PEO-PPO-PEO crosslinked with trifunctional urethane,poly(bis(methoxy-ethoxy-ethoxide))-phosphazene (MEEP), triol-type PEOcrosslinked with difunctional urethane,poly((oligo)oxyethylene)methacrylate-co-alkali metal methacrylate,polyacrylonitrile (PAN), polymethylmethacrylate (PMMA),polymethylacrylonitrile (PMAN), polysiloxanes and their copolymers andderivatives, acrylate-based polymer, other similar solvent-freepolymers, combinations of the foregoing polymers either condensed orcross-linked to form a different polymer, and physical mixtures of anyof the foregoing polymers. Other less conductive polymers that may beused in combination with the above polymers to improve the strength ofthin laminates include: polyester (PET), polypropylene (PP),polyethylene naphthalate (PEN), polyvinylidene fluoride (PVDF),polycarbonate (PC), polyphenylene sulfide (PPS), andpolytetrafluoroethylene (PTFE). Such solid polymer electrolytes mayfurther include a small amount of organic solvents listed above. Thepolymer electrolyte may be an ionic liquid polymer. Such polymer-basedelectrolytes can be coated using any number of conventional methods suchas curtain coating, slot coating, spin coating, inkjet coating, spraycoating or other suitable method.

Additives may be included in the electrolyte to serve various functions.For example, additives such as polymerizable compounds having anunsaturated double bond may be added to stabilize or modify the SEI.Certain amines or borate compounds can act as cathode protection agents.Lewis acids can be added to stabilize fluorine-containing anion such asPF₆ ⁻. Safety protection agents include those to protect overcharge,e.g., anisoles, or act as fire retardants, e.g., alkyl phosphates.

In some embodiments, the original, non-cycled anode may undergostructural or chemical changes during electrochemicalcharging/discharging, for example, from normal battery usage or from anearlier “electrochemical formation step”. As is known in the art, anelectrochemical formation step is commonly used to form an initial SEIlayer and involves relatively gentle conditions of low current andlimited voltages. The modified anode prepared in part from suchelectrochemical charging/discharging cycles may still have excellentperformance properties, despite such structural and/or chemical changesrelative to the original, non-cycled anode.

Although the present anodes have been discussed with reference tobatteries, in some embodiments the present anodes may be used in hybridcapacitor devices. Relative to conventional anodes, the anodes of thepresent disclosure may have one or more of at least the followingunexpected advantages: comparable or improved stability at aggressive≥1C charging rates; higher overall areal charge capacity; highergravimetric charge capacity; higher volumetric charge capacity; improvedphysical durability; simplified manufacturing process; and/or a morereproducible manufacturing process.

Some non-limiting representative embodiments are listed below.

1. An anode for an energy storage device comprising:

-   -   a current collector comprising:        -   i) an electrically conductive substrate comprising a first            electrically conductive material,        -   ii) a plurality of electrically conductive structures in            electrical communication with the electrically conductive            substrate, wherein each electrically conductive structure of            the plurality of electrically conductive structures            comprises a second electrically conductive material; and        -   iii) a metal oxide coating comprising:            -   a) a first metal oxide material in contact with the                electrically conductive substrate; or            -   b) a second metal oxide material in contact with the                plurality of electrically conductive structures; or            -   c) both (a) and (b); and    -   a lithium storage coating overlaying and in contact with the        metal oxide coating, wherein the lithium storage coating        comprises a total content of silicon, germanium, or a        combination thereof, of at least 40 atomic %; and    -   wherein the plurality of electrically conductive structures are        at least partially embedded within the lithium storage coating.

2. The anode of embodiment 1, wherein the first electrically conductivematerial comprises a metal or a conductive carbon.

3. The anode of embodiment 1 or 2, wherein the first electricallyconductive material comprises a transition metal.

4. The anode of embodiment 3, wherein the transition metal is copper,nickel, iron, chromium, or titanium.

5. The anode according to any of embodiments 1-4, wherein the firstelectrically conductive material comprises stainless steel.

6. The anode according to any of embodiments 1-5, wherein theelectrically conductive substrate is in the form of a sheet, a foil, ora mesh.

7. The anode of embodiment 1, wherein the electrically conductivesubstrate comprises a copper foil or mesh, a nickel foil or mesh, astainless steel foil or mesh, or a conductive carbon sheet or mesh.

8. The anode of embodiment 7, wherein the conductive carbon comprisesbundled carbon nanotubes.

9. The anode according to any of embodiments 1-6, further comprising anelectrically conductive layer and an insulating support, wherein theelectrically conductive substrate comprises the electrically conductivelayer provided over the insulating support.

10. The anode according to any of embodiments 1-9, wherein the secondelectrically conductive material comprises a conductive carbon.

11. The anode according to any of embodiments 1-10, wherein the secondelectrically conductive material comprises carbon nanotubes.

12. The anode according to any of embodiments 1-11, wherein the secondelectrically conductive material comprises a metal.

13. The anode according to any of embodiments 1-12, wherein the secondelectrically conductive material comprises a transition metal.

14. The anode of embodiment 13, wherein the transition metal is copper,nickel, or titanium.

15. The anode of any of embodiments 1-14, wherein the second conductivematerial comprises a metal silicide.

16. The anode according to any of embodiments 1-15, wherein eachelectrically conductive structure of the electrically conductivestructures is characterized as having a width measured parallel to theelectrically conductive substrate surface and a height extending awayfrom, and measured normal to, the electrically conductive substratesurface, the ratio of height to width defining an aspect ratio, whereinthe aspect ratio is greater than 1.

17. The anode of embodiment 16, wherein the aspect ratio is at least 3.

18. The anode of embodiment 16 or 17, wherein the height is at least 1μm.

19. The anode according to any of embodiments 16-18, wherein the heightis in a range of about 2 μm to about 20 μm.

20. The anode according to any of embodiments 1-19, wherein at least oneof the electrically conductive structures is in the form of a wire,pillar, tube, ridges, or dendrite.

21. The anode according to any of embodiments 1-20, wherein at least oneof the electrically conductive structures is a nanowire or a nanotube.

22. The anode according to any of embodiments 1-21, wherein theelectrically conductive structures are provided in a non-random patternover the electrically conductive substrate.

23. The anode according to any of embodiments 1-22, wherein theelectrically conductive structures are provided in a random pattern overthe electrically conductive substrate.

24. The anode according to any of embodiments 1-23, wherein 2% to 80% ofthe surface area of the electrically conductive substrate is in contactwith the plurality of electrically conductive structures.

25. The anode according to any of embodiments 1-24, wherein the secondelectrically conductive material is substantially the same as the firstelectrically conductive material.

26. The anode according to any of embodiments 1-24, wherein the secondelectrically conductive material is different than the firstelectrically conductive material.

27. The anode according to any of embodiments 1-26, wherein the currentcollector does not include the first metal oxide material in contactwith the electrically conductive substrate.

28. The anode according to any of embodiments 1-26, wherein the currentcollector does not include the second metal oxide material in contactwith the plurality of electrically conductive structures.

29. The anode according to any of embodiments 1-26, wherein the currentcollector includes the first metal oxide material and the second metaloxide material.

30. The anode of any of embodiments 27-29, wherein the first metal oxidematerial and the second metal oxide material comprise substantially thesame elemental composition.

31. The anode of any of embodiments 27-29, wherein the first metal oxidematerial and the second metal oxide material comprise differentelemental compositions.

32. The anode according to any of embodiments 1-31, wherein the firstmetal oxide material comprises a transition metal oxide.

33. The anode according to embodiment 32, wherein the transition metaloxide comprises an oxide of nickel or titanium.

34. The anode according to embodiment 32 or 33, wherein the electricallyconductive substrate comprises a metal, and the first metal oxidecomprises an oxide of the metal.

35. The anode according to any of embodiments 1-26 or 28-34, wherein thefirst metal oxide coating has an average thickness of at least 0.005 μm.

36. The anode of embodiment 35, wherein the first metal oxide materialhas an average thickness in a range of 0.02 to 2.0 μm.

37. The anode according to any of embodiments 1-27 or 29-31, wherein thesecond metal oxide material comprises a transition metal oxide.

38. The anode according to embodiment 37, wherein the transition metaloxide comprises an oxide of nickel or titanium.

39. The anode according to embodiment 37 or 38, wherein the electricallyconductive substrate comprises a metal, and the second metal oxidecomprises an oxide of the metal.

40. The anode according to any of embodiments 1-27 or 29-39, wherein thesecond metal oxide material has an average thickness of at least 0.002μm.

41. The anode according to any of embodiments 1-26 or 29-40, wherein thesecond metal oxide material has an average thickness less than theaverage thickness of the first metal oxide material.

42. The anode of embodiment 40 or 41, wherein the second metal oxidematerial has a thickness in a range of 0.01 to 1.0 μm.

43. The anode according to any of embodiments 1- 42, wherein the lithiumstorage coating is porous.

44. The anode according to any of embodiments 1-43, wherein the lithiumstorage coating comprises at least 85 atomic % amorphous silicon, thelithium storage coating having a density in a range of about 1.1 g/cm³to 2.2 g/cm³.

45. The anode according to any of embodiments 1-44, wherein the lithiumstorage coating has a thickness of at least 3 μm.

46. The anode according to any of embodiments 1-45, wherein the lithiumstorage coating has a thickness in a range of about 7μm to about 30 μm.

47. The anode according to any of embodiments 1-46, further comprisinglithium storage nanostructures in contact with the electricallyconductive structures.

48. The anode of embodiment 47, wherein the current collector does notinclude the second metal oxide material.

49. The anode according to any of embodiments 1-46, further comprisinglithium storage nanostructures in contact with the electricallyconductive substrate.

50. The anode of embodiment 49, wherein the current collector does notinclude the first metal oxide material.

51. A method of making an anode for an energy storage device, the methodcomprising:

-   -   providing a current collector precursor comprising an        electrically conductive substrate comprising i) a first        electrically conductive material and ii) a plurality of        electrically conductive structures in electrical communication        with the electrically conductive substrate, wherein each        electrically conductive structure of the plurality of        electrically conductive structures comprises a second        electrically conductive material;    -   forming a current collector by:        -   a) forming a first metal oxide material in contact with the            electrically conductive substrate; or        -   b) forming a second metal oxide material in contact with the            plurality of electrically conductive structures; or        -   c) both (a) and (b); and    -   depositing by a CVD process a lithium storage coating over the        current collector, the lithium storage coating overlaying the        first metal oxide coating, the second metal oxide coating, or        both, wherein the plurality of electrically conductive        structures are at least partially embedded within the lithium        storage coating, and    -   wherein the lithium storage coating comprises a total content of        silicon, germanium, or a combination thereof, of at least 40        atomic %.

52. The method of embodiment 51, wherein forming the first metal oxidematerial comprises oxidation of a portion of the electrically conductivesubstrate surface.

53. The method of embodiment 51 or 52, wherein forming the second metaloxide material comprises oxidation of a portion of the plurality ofelectrically conductive structures.

54. The method of embodiment 51, wherein forming the first metal oxidematerial comprises deposition by ALD, physical vapor deposition, or aCVD process.

55. The method of embodiment 51 or 52, wherein forming the second metaloxide material comprises deposition by ALD, physical vapor deposition,or a CVD process.

56. The method according to any of embodiments 51-55, wherein the firstelectrically conductive material comprises a metal or a conductivecarbon.

57. The method according to any of embodiments 51-56, wherein the firstconductive material comprises a transition metal.

58. The method of embodiment 57, wherein the transition metal is copper,nickel, iron, chromium, or titanium.

59. The method according to any of embodiments 51-58, wherein the firstconductive material comprises stainless steel.

60. The method according to any of embodiments 51-59, wherein theelectrically conductive substrate is in the form of a sheet, a foil, ora mesh.

61. The method according to any of embodiments 51-60, wherein the secondconductive material comprises a conductive carbon.

62. The method according to any of embodiments 51-61, wherein the secondconductive material comprises carbon nanotubes.

63. The method according to any of embodiments 51-62, wherein the secondconductive material comprises a metal.

64. The method according to any of embodiments 51-63, wherein the secondconductive material comprises a transition metal.

65. The method of embodiment 64, wherein the transition metal is copper,nickel, or titanium.

66. The method according to any of embodiments 51-65, wherein the secondconductive material comprises a metal silicide.

67. The method of according to any of embodiments 51-66, furthercomprising patterned depositing the plurality of electrically conductivestructures over the surface of the electrically conductive substrate toform the current collector precursor, wherein each electricallyconductive structure of the plurality of electrically conductivestructures comprises a metal.

68. The method according to any of embodiments 51-68, wherein the firstelectrically conductive material is substantially the same as the secondelectrically conductive material.

69. The method according to any of embodiments 51-68, wherein the firstelectrically conductive material and the second electrically conductivematerial both comprise copper.

70. The method of embodiment 70, wherein first electrically conductivematerial is different than the second electrically conductive material.

71. The method of embodiment 67, wherein the patterned depositingcomprises electroplating, electroless plating, physical vapordeposition, or a CVD process.

72. The method of embodiment 71, further comprising photolithographicmethods as part of the patterned depositing.

73. The method of according to any of embodiments 51-69, furthercomprising etching patterned portions of the electrically conductivesubstrate to form the plurality of electrically conductive structures ofthe current collector precursor, wherein the electrically conductivesubstrate comprises a metal, and wherein each electrically conductivestructure of the plurality of electrically conductive structurescomprises the metal.

74. The method according to any of embodiments 51-73, wherein thelithium storage coating comprises at least 85 atomic % amorphoussilicon, the lithium storage coating having a density in a range ofabout 1.1 g/cm³ to 2.2 g/cm³.

75. The method according to any of embodiments 51-74, wherein thelithium storage coating has a thickness of at least 3 μm.

76. The method according to any of embodiments 51-75, wherein the CVDprocess is a PECVD process.

77. A lithium-ion battery comprising the anode according to any ofembodiment 1-50 and a cathode.

78. A lithium-ion battery comprising the anode made according to any ofembodiments 51-75 and a cathode.

79. The lithium-ion battery of embodiment 77 or 78, wherein the anode isprelithiated and the cathode comprises sulfur, selenium, or both sulfurand selenium.

The specific details of particular embodiments may be combined in anysuitable manner without departing from the spirit and scope ofembodiments of the invention. However, other embodiments of theinvention may be directed to specific embodiments relating to eachindividual aspect, or specific combinations of these individual aspects.

The above description of example embodiments of the invention has beenpresented for the purposes of illustration and description. It is notintended to be exhaustive or to limit the invention to the precise formdescribed, and many modifications and variations are possible in lightof the teaching above.

In the preceding description, for the purposes of explanation, numerousdetails have been set forth in order to provide an understanding ofvarious embodiments of the present technology. It will be apparent toone skilled in the art, however, that certain embodiments may bepracticed without some of these details, or with additional details.

Having described several embodiments, it will be recognized by those ofskill in the art that various modifications, alternative constructions,and equivalents may be used without departing from the spirit of theinvention. Additionally, a number of well-known processes and elementshave not been described in order to avoid unnecessarily obscuring thepresent invention. Additionally, details of any specific embodiment maynot always be present in variations of that embodiment or may be addedto other embodiments.

Where a range of values is provided, it is understood that eachintervening value, to the tenth of the unit of the lower limit unlessthe context clearly dictates otherwise, between the upper and lowerlimits of that range is also specifically disclosed. Each smaller rangebetween any stated value or intervening value in a stated range and anyother stated or intervening value in that stated range is encompassed.The upper and lower limits of these smaller ranges may independently beincluded or excluded in the range, and each range where either, neither,or both limits are included in the smaller ranges is also encompassedwithin the invention, subject to any specifically excluded limit in thestated range. Where the stated range includes one or both of the limits,ranges excluding either or both of those included limits are alsoincluded.

As used herein and in the appended claims, the singular forms “a”, “an”,and “the” include plural referents unless the context clearly dictatesotherwise. Thus, for example, reference to “a method” includes aplurality of such methods and reference to “the layer” includesreference to one or more layers and equivalents thereof known to thoseskilled in the art, and so forth. The invention has now been describedin detail for the purposes of clarity and understanding. However, itwill be appreciated that certain changes and modifications may bepracticed within the scope of the appended claims.

All publications, patents, and patent applications cited herein arehereby incorporated by reference in their entirety for all purposes.None is admitted to be prior art.

We claim:
 1. An anode for an energy storage device comprising: a currentcollector comprising: i) an electrically conductive substrate comprisinga first electrically conductive material; ii) a plurality ofelectrically conductive structures in electrical communication with theelectrically conductive substrate, wherein each electrically conductivestructure of the plurality of electrically conductive structurescomprises a second electrically conductive material; and iii) a metaloxide coating comprising: a) a first metal oxide material in contactwith the electrically conductive substrate; or b) a second metal oxidematerial in contact with the plurality of electrically conductivestructures; or c) both (a) and (b); and a lithium storage coatingoverlaying and in contact with the metal oxide coating, wherein thelithium storage coating comprises a total content of silicon, germanium,or a combination thereof, of at least 40 atomic %; and wherein theplurality of electrically conductive structures are at least partiallyembedded within the lithium storage coating.
 2. The anode of claim 1,wherein the first electrically conductive material comprises copper,nickel, iron, chromium, or titanium.
 3. The anode of claim 1, whereinthe electrically conductive substrate comprises a copper foil or mesh, anickel foil or mesh, a stainless steel foil or mesh, or a conductivecarbon sheet or mesh.
 4. The anode of claim 1, wherein the secondelectrically conductive material comprises a conductive carbon.
 5. Theanode of claim 1, wherein the second electrically conductive materialcomprises copper, nickel, or titanium.
 6. The anode of claim 1, whereineach electrically conductive structure of the electrically conductivestructures is characterized as having a width measured parallel to theelectrically conductive substrate surface and a height extending awayfrom, and measured normal to, the electrically conductive substratesurface, the ratio of height to width defining an aspect ratio, whereinthe aspect ratio is greater than 3 and the height is at least 1 μm. 7.The anode of claim 1, wherein at least one of the electricallyconductive structures is in the form of a wire, pillar, tube, ridge, ordendrite.
 8. The anode of claim 1, wherein the electrically conductivestructures are provided in a non-random pattern over the electricallyconductive substrate.
 9. The anode of claim 1, wherein 2% to 80% of thesurface area of the electrically conductive substrate is in contact withthe plurality of electrically conductive structures.
 10. The anode ofclaim 1, wherein the current collector does not include one of the firstmetal oxide material in contact with the electrically conductivesubstrate or the second metal oxide material in contact with theplurality of electrically conductive structures.
 11. The anode of claim1, wherein the current collector includes both the first metal oxidematerial in contact with the electrically conductive substrate and thesecond metal oxide material in contact with the plurality ofelectrically conductive structures.
 12. The anode of claim 1, wherein atleast one of the first metal oxide material or the second metal oxidematerial comprises an oxide of a transition metal.
 13. The anode ofclaim 12, wherein at least one of the first metal oxide material or thesecond metal oxide material comprises an oxide of nickel or an oxide oftitanium.
 14. The anode of claim 1, wherein the first metal oxidematerial in contact with the electrically conductive substrate has anaverage thickness in a range of 0.02 to 2.0 μm.
 15. The anode of claim1, wherein the second metal oxide material in contact with theelectrically conductive substrate has a thickness in a range of 0.01 to1.0 μm.
 16. The anode of claim 1, wherein the lithium storage coating isporous and comprises at least 85 atomic % amorphous silicon, the lithiumstorage coating having a density in a range of 1.1 g/cm³ to 2.2 g/cm³.17. The anode of claim 1, wherein the lithium storage coating has athickness of at least 3 μm.
 18. The anode of claim 1, further comprisinglithium storage nanostructures in contact with the plurality ofelectrically conductive structures or the electrically conductivesubstrate.
 19. A lithium-ion battery comprising the anode of claim 1 anda cathode.
 20. The lithium-ion battery of claim 19, wherein the anode isprelithiated and the cathode comprises sulfur, selenium, or both sulfurand selenium.